Electron beam apparatuses, in particular a scanning electron microscope (also referred to as SEM below) and/or a transmission electron microscope (also referred to as TEM below), are used to examine objects (also referred to as samples) in order to obtain knowledge in respect of the properties and behaviors of the objects under certain conditions.
In an SEM, an electron beam (also referred to as primary electron beam below) is generated by means of a beam generator and focused on an object to be examined by way of a beam guiding system. An objective lens is used for focusing purposes. The primary electron beam is guided in a grid-shaped manner over a surface of the object to be examined by way of a deflection device. Here, the electrons of the primary electron beam interact with the object to be examined. In particular interaction particles and/or interaction radiation is/are generated as a result of the interaction. By way of example, the interaction particles are electrons. In particular, electrons are emitted by the object—the so-called secondary electrons—and electrons of the primary electron beam are scattered back—the so-called backscattered electrons. The interaction particles form the so-called secondary beam and are detected by at least one particle detector. The particle detector generates detection signals which are used to generate an image of the object.
An imaging of the object to be examined is thus obtained.
By way of example, the interaction radiation is x-ray radiation or cathodoluminescence. It is detected for example with a radiation detector and is used in particular for examining the material composition of the object.
In the case of a TEM, a primary electron beam is likewise generated by means of a beam generator and focused on an object to be examined by means of a beam guiding system. The primary electron beam passes through the object to be examined. When the primary electron beam passes through the object to be examined, the electrons of the primary electron beam interact with the material of the object to be examined. The electrons passing through the object to be examined are imaged onto a luminescent screen or onto a detector—for example in the form of a camera—by a system comprising an objective. By way of example, the aforementioned system additionally also comprises a projection lens. Here, imaging may also take place in the scanning mode of a TEM. As a rule, such a TEM is referred to as STEM. Additionally, provision can be made for detecting electrons scattered back at the object to be examined and/or secondary electrons emitted by the object to be examined by means of a further detector in order to image an object to be examined.
The integration of the function of an STEM and an SEM in a single particle beam apparatus is known. It is therefore possible to carry out examinations of objects with an SEM function and/or with an STEM function using this particle beam apparatus.
Furthermore, the prior art has disclosed the practice of analyzing and/or processing an object in a particle beam apparatus using, on the one hand, electrons and, on the other hand, ions. By way of example, an electron beam column having the function of an SEM is arranged at the particle beam apparatus. Additionally, an ion beam column is arranged at the particle beam apparatus. Ions used for processing an object are generated by means of an ion beam generator arranged in the ion beam column. By way of example, material of the object is ablated or material is applied onto the object during the processing. The ions are additionally or alternatively used for imaging. The electron beam column with the SEM function serves, in particular, for examining further the processed or unprocessed object, but also for processing the object.
The above-mentioned particle beam apparatuses of the prior art each have a sample chamber in which an object that is to be analyzed and/or processed is arranged on a sample stage. It is furthermore known to arrange a plurality of different objects simultaneously at the sample stage so as to analyze and/or process them one after the other using the respective particle beam apparatus that has the sample chamber. The sample stage is embodied to be movable so as for positioning the object or objects in the sample chamber. A relative position of the object or objects with respect to an objective lens is set, for example. A known sample stage is embodied to be movable in three directions which are arranged perpendicular to one another. Moreover, the sample stage can be rotated about two rotational axes which are arranged perpendicular to one another.
It is known to operate the sample chamber in different pressure ranges. For example, the sample chamber is operated in a first pressure range or in a second pressure range. The first pressure range comprises only pressures of less than or equal to 10−3 hPa, and the second pressure range comprises only pressures of greater than 10−3 hPa. To ensure said pressure ranges, the sample chamber is vacuum-sealed during an examination of the object or objects with the particle beam apparatus. For this reason, free view of the object or objects is therefore not easily possible.
To ensure view of the object or objects and to be able to position the object or objects in a controlled fashion using the sample stage, it is known to use an imaging device for imaging the object or objects and for generating an image of the object or objects. It is furthermore known to use the imaging device for imaging a structural unit of the particle beam apparatus. The structural unit is arranged, for example, in the sample chamber of the particle beam apparatus. The structural unit is in particular embodied in the form of a gas injection system, a micromanipulator, a detector that is embodied to be movable and/or a charge compensation unit. The known imaging device has a camera that is mounted at the sample chamber or in the sample chamber and images the object, the objects and/or the structural unit. It is thus possible, for example, to observe and set in a controlled manner the position of the object, the objects and/or the structural unit by observing the images generated by the camera. Two imaging devices are known from the prior art, which will be explained below.
The first known imaging device permits observation of an object and/or a structural unit, arranged at the sample stage, during a simultaneous imaging or processing of the object with the primary particle beam of a particle beam apparatus. In other words, the first imaging device permits observation of the object and/or the structural unit using the camera, while the primary particle beam is focused onto the object and while interaction particles and/or interaction radiation is/are detected using a detector or a plurality of detectors. The first imaging device has an illumination unit that generates infrared light. It is known to use infrared light having a wavelength of 950 nm. The infrared light is used to illuminate the object and/or the structural unit. The object and/or the structural unit is/are imaged using the camera which is sensitive to infrared light. The images of the object generated due to the imaging by way of the camera are then used to observe the object. Furthermore, the images of the structural unit generated due to the imaging by way of the camera are then used to observe the structural unit. The first known imaging device permits imaging of the object or the structural unit using the camera and simultaneous examination of the object with the primary particle beam of the particle beam apparatus, since the detector or the plurality of detectors for detecting the interaction particles and/or interaction radiation are influenced by the infrared light only to a minor extent, with the result that sufficient function of the detector or the plurality of detectors continues to be ensured. However, the first known imaging device has the disadvantage that only black-and-white images are generated using the camera of the first known imaging device. Color differences on the objects, object regions or structural units cannot be identified on the image generated with the first known imaging device. Color information that the object or the structural unit has/contains cannot be identified in the black-and-white image either.
The second known imaging device does not generate black-and-white images, but color images of an object arranged in the sample chamber at the sample stage, or color images of a structural unit that is arranged in the sample chamber. The second known imaging device has an illumination unit that is arranged at the sample chamber and introduces white light into the sample chamber. This white light is used to illuminate the object and/or the structural unit. A camera images the object and generates color images of the object. The camera additionally or alternatively images the structural unit and generates color images of the structural unit. However, imaging of the object or of the structural unit using the second known imaging device (and thus the generation of a color image) and detection of interaction particles and/or interaction radiation are not simultaneously possible, or are simultaneously possible only if the detectors for detecting the interaction particles/interaction radiation are arranged, connected and/or embodied in the particle beam apparatus such that they are not disturbed, or disturbed only to a minor extent, by the white light from the illumination unit. Generally, the second known imaging device is used only to generate a recording of an overview image in color, which can no longer be updated during the detection of the interaction particles and/or interaction radiation.
Accordingly, it is desirable to be able to specify an imaging device and a particle beam apparatus having such an imaging device which permits the recording and generation of images of an object or of a structural unit in a sample chamber of a particle beam apparatus in every operating state of the particle beam apparatus.